1. Field of the Invention
The present invention relates to a gas insulated switchgear and to a method for detecting arc damage in a part used in a gas insulated switchgear, and more particularly, to a gas insulated switchgear and a method for detecting arc damage in a gas insulated switchgear part, which detect easily when an electric contact reaches an originally set wear limit.
2. Description of the Related Art
Electrical contacts for switching an electric circuit are built into power equipment such as high-voltage circuit breakers, disconnectors or switches in power stations and/or substations. In the wake of the trend in recent years towards more compact power equipment, with a view to increasing economic efficiency and environmental compatibility, electric contacts tend to become smaller, but on the other hand, power equipment must cope with ever higher voltages and capacities, as a result of increased power demand, all of which results in smaller electric contacts supporting greater current densities.
In such power equipment, circuit breaking occurs repeatedly under high voltage, whereby the electric contacts vaporize and wear down as a result of the arc heat generated upon switching. Therefore it has been extremely important heretofore to grasp accurately the wear limit in an electric contact, to afford proper operation of the electric contact and to increase the utilization rate of the power equipment.
Methods for detecting the wear limit of an electric contact include, for instance, a method for detecting magnetic changes using a magnet mounted on a brush (Japanese Unexamined Patent Application Laid-open No. H06-14501), a method for monitoring voltage changes in a piezoelectric element mounted on an electric contact, and a method for detecting abnormal vibration or the like through mounting of a vibration sensor and/or an acceleration sensor on a switch (Japanese Unexamined Patent Application Laid-open Nos. H10-241481 and H11-354341). In these methods, a monitoring device detects anomalies by arranging a sensor or the like in the vicinity of a contact and by measuring changes in electric or mechanical characteristics.
A method has also been proposed in which wear can be detected, without mounting any special sensor or the like, by analyzing the light generated by the electrodes themselves during arc formation (Japanese Unexamined Patent Application Laid-open No. 2005-71727).
Conventional monitoring devices, such as those disclosed in Japanese Unexamined Patent Application Laid-open Nos. H06-14501, H10-241481 and H11-354341 measure deformation or changes in mechanical characteristics that are attributable to wear, at the initial stage of an anomaly. However, direct detection of wear limit of electrodes, nozzles or the like remained difficult in such monitoring devices.
The method in Japanese Unexamined Patent Application Laid-open No. 2005-71727, although suitable for detecting electrode wear, failed to detect wear of electrode-peripheral parts in a switch, such as a nozzle or the like.